(flāj'ə-lāt') Any of various protozoans of the subphylum Mastigophora that move by means of one or more flagella. Some flagellates can make food by photosynthesis (such as euglenas and volvox), and are often classified as green algae by botanists. Others are symbiotic or parasitic (such as trypanosomes). Flagellates are related to amoebas. Also called mastigophoran.